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Pfletschinger H.,TU Darmstadt | Engelhardt I.,TU Darmstadt | Piepenbrink M.,TU Darmstadt | Koniger F.,Institute of Functional Interfaces | And 3 more authors.
Environmental Earth Sciences | Year: 2012

For the determination of groundwater recharge processes in arid environments, vadose zone water fluxes and water storage should be considered. To better understand and quantify vadose zone processes influencing groundwater recharge, a soil column experimental setup has been developed that mimics arid atmospheric conditions and measures water and temperature fluxes in high temporal and spatial resolution. The focus of the experiment was on the determination of water infiltration, redistribution, evaporation and percolation under non-isothermal conditions. TDR rod sensors and a specific TDR "Taupe" cable sensor were used for water content measurements and allowed the infiltration fronts to be traced over the whole column length. Applying single irrigations of different amount and intensity showed the applicability of the experimental setup for the measurement of water movement in the unsaturated soil column. © 2011 Springer-Verlag.


News Article | February 15, 2017
Site: www.eurekalert.org

Researchers of Karlsruhe Institute of Technology (KIT) have made major progress in the production of two-dimensional polymer-based materials. To produce cloths from monomolecular threads, the scientists used SURMOFs, i.e. surface-mounted metal-organic frameworks, developed by KIT. They inserted four-armed monomers, i.e. smaller molecular building blocks, into some SURMOF layers. Cross-linking of the monomers then resulted in textiles consisting of interwoven polymer threads. This work is now presented in Nature Communications. (DOI: 10.1038/ncomms14442) Self-organized cross-linking of polymer threads, i.e. of extremely long molecules, to two-dimensional tissues is a big challenge in polymer chemistry. With the help of a bottom-up process to cross-link smaller molecules, so-called monomers, scientists of the Institute of Functional Interfaces (IFG) and Institute of Nanotechnology (INT) of KIT now made an important step towards reaching this objective. They produced a tissue from monomolecular polymer threads by using SURMOFs, i.e. surface-mounted metal-organic frameworks, as looms. This approach is now presented in Nature Communications. The SURMOFs developed by IFG are frameworks consisting of metallic node points and organic linkers that are assembled on a substrate layer by layer. They have a crystalline structure and can be customized to a large range of the applications by combining various materials and varying the pore sizes. For weaving two-dimensional textiles, the KIT scientists specifically inserted special connection elements, i.e. four-armed monomers, into the SURMOF layers for later cross-linking. Then, these active SURMOF layers were embedded between so-called sacrificial layers. "In this way, we produced a sandwich-type setup to ensure that the textiles produced really are two-dimensional, which means that they have a thickness of one molecule layer only," Professor Christof Wöll says. He heads the IFG and is the corresponding author of the publication together with Professor Marcel Mayor of INT. The scientists then applied a catalyst in these active SURMOF layers to start a reaction for linking the monomers to polymers. Afterwards, the metallic node points were removed. Flat tissues of monomolecular polymer threads remained. "The polymer threads are kept together by the mechanical forces resulting from the weave pattern," Marcel Mayor explains. "Hence, the molecular tissues are as flexible as textiles produced in a conventional way." For further information, please contact: Margarete Lehné, Media Relations Officer, Phone: 49-721-608-4 8121, Fax: +49 721 608-4 3658, Email: margarete.lehne@kit.edu Karlsruhe Institute of Technology (KIT) pools its three core tasks of research, higher education, and innovation in a mission. With about 9,300 employees and 25,000 students, KIT is one of the big institutions of research and higher education in natural sciences and engineering in Europe. KIT - The Research University in the Helmholtz Association Since 2010, the KIT has been certified as a family-friendly university. This press release is available on the internet at http://www. .


Biologist Johannes Eberhard Reiner, KIT, with the reactors for microbial electro-synthesis. Credit: Constanze Zacharias Researchers of Karlsruhe Institute of Technology (KIT) are working on an efficient and inexpensive method for the production of organic plastics. In the "BioElectroPlast" project funded by the Federal Ministry of Research they use microorganisms that produce polyhydroxybutyric acid from flue gas, air, and renewable power. The optimized process of microbial electrosynthesis opens up further perspectives for the future production of biofuel or for the storage of power from regenerative sources in the form of chemical products, for instance. The consumer's wish for sustainable products also increases the demand for organic plastics, for e.g. disposable cups, packages or garbage bags. The "BioElectroPlast" project coordinated by the Applied Biology Group headed by Professor Johannes Gescher of KIT's Institute for Applied Biosciences (IAB) focuses on a method to produce organic plastics with a minimum consumption of resources and at low costs. In addition, "BioElectroPlast" is aimed at using the greenhouse gas carbon dioxide (CO2) as an inexpensive and generally available raw material in the chain of values added and at applying renewable power. For this purpose, the scientists use a relatively new technology, called microbial electrosynthesis. About six years ago, researchers in the USA for the first time described how certain microorganisms grow on a cathode, bind CO2, and use the cathode as the only energy and electron source. A chemical process, by contrast, requires high pressures and temperatures and, hence, a high energy input as well as expensive catalysts. So far, microbial electrosynthesis has been used mainly to produce acetates – salts of acetic acid. "We have optimized the process, such that the microorganisms are supplied with more energy for the production of molecules of higher complexity, e.g. polymers," Johannes Eberhard Reiner of the IAB explains. "We mix the CO2 with air. Then, the microorganisms use the oxygen as electron acceptor. This is quite similar to human breathing, where oxygen also serves as electron acceptor. In human beings, however, electrons do not come from a cathode, but are released by metabolization of our food in the cells. Then, they are transferred to the oxygen for energy production." As biocatalyst, the researchers use a newly isolated microorganism that permanently regenerates itself. Flue gas is applied as CO2 source. As a result, the concentration of this greenhouse gas is reduced and other sources of organic carbon that are usually applied as biotechnological substrates, such as agricultural products, are no longer required. Competition with food and feed production is avoided. The electric power needed for the "Bio-ElectroPlast" process is based on regenerative sources. The Federal Ministry of Education and Research (BMBF) funds the "BioElectroPlast" project under its initiative "CO2Plus – Material Use of CO2 to Broaden the Raw Materials Base". "BioElectroPlus" started in September this year and is scheduled for a duration of three years. Apart from the IAB, the KIT project partners are the Chair for Water Chemistry and Water Technology of Professor Harald Horn at the Engler-Bunte Institute (EBI) and the "Microbial Bioinformatics" Group headed by Dr. Andreas Dötsch at the Institute of Functional Interfaces (IFG). The other partners are the University of Freiburg and EnBW AG. EnBW participates in the project to further reduce CO2 emission of coal combustion as a bridge technology. The researchers plan to test their reactors directly in the coal-fired power plant of EnBW in Karlsruhe and to use the exhaust gases produced there. In parallel to the "BioElectroPlast" project, KIT's researchers also study the conversion of carbon dioxide into valuable compounds under the industry-funded ZeroCarb FP innovation alliance. Here, the scientists use alternative biocatalysts isolated by them, as the industry partners Südzucker AG and B.R.A.I.N. AG have specified different process requirements and concentrate on other end products. Explore further: Microorganisms in cow manure used to build rechargeable battery


Obst U.,Institute of Functional Interfaces | Marten S.-M.,Institute of Functional Interfaces | Niessner C.,Albert Ludwigs University of Freiburg | Hartwig E.,Albert Ludwigs University of Freiburg
International Journal of Artificial Organs | Year: 2011

Bacterial 16S rDNA was monitored and identified from orthopedic metallic implants after routine or septic removal from patients in a German hospital. From March to June 2009, 28 metallic implants, 10 human biopsies, and 6 foam dressings from 28 patients were investigated. After analysis of this first collective, the methods were optimized to enhance sensitivity and to reduce interference with human DNA. Then a second collective consisting of 21 metallic implants from 21 patients was investigated from June 2009 to January 2010. In the first collective, 71% of the metallic implants were negative for eubacterial DNA. Pathogens such as Staphylococcus aureus and opportunists such as Lactobacillus rhamnosus were identified in 11% of the samples, whereas the residual 18% positive results were classified as from skin sources or could not be confirmed. Tissue, secretion, and bone samples as well as foam dressings from the same collective also contained pathogens and opportunists. After the optimization of the methods, a considerable increase of positive samples was seen: in the second collective 19 of the 21 metallic implants proved to be positive for eubacterial 16S rDNA. Bacterial DNA from environmental sources was detected in 13 samples, and in 20 specimens, predominantly mostly the skin. Opportunistic pathogens were detected in 19 samples. Interestingly, septic complications did not occur despite the presence of bacterial DNA. The results obtained up to now encourage us not only to continue a directed monitoring of bacterial DNA on orthopedic implants in practice but also to look intensely for possible sources of bacterial contamination during and after insertion or during removal of such implants. © 2011 Wichtig Editore.


Li J.,Institute of Toxicology and Genetics | Li J.,University of Heidelberg | Kleintschek T.,Institute of Functional Interfaces | Rieder A.,Institute of Functional Interfaces | And 6 more authors.
ACS Applied Materials and Interfaces | Year: 2013

Biofilms represent a fundamental problem in environmental biology, water technology, food hygiene as well as in medical and technical systems. Recently introduced slippery liquid-infused porous surface (SLIPS) showed great promise for preventing biofilm formation owing to the low surface energy of such surface in combination with its self-cleaning properties. In this study we demonstrated a novel hydrophobic liquid-infused porous poly(butyl methacrylate-co-ethylene dimethacrylate) surface (slippery BMA-EDMA) with bacteria-resistance in BM2 mineral medium and long-term stability in aqueous environments. We showed that the slippery BMA-EDMA surface prevents biofilm formation of different strains of opportunistic pathogen Pseudomonas aeruginosa for at least up to 7 days in low nutrient medium. Only ∼1.8% of the slippery surface was covered by the environmental P. aeruginosa PA49 strain under investigation. In uncoated glass controls the coverage of surfaces reached ∼55% under the same conditions. However, in high nutrient medium, more relevant to physiological conditions, the biofilm formation on the slippery surface turned out to be highly dependent on the bacterial strain. Although the slippery surface could prevent biofilm formation of most of the P. aeruginosa strains tested (∼1% surface coverage), the multiresistant P. aeruginosa strain isolated from wastewater was able to cover up to 12% of the surface during 7 days of incubation. RAPD-PCR analysis of the used P. aeruginosa strains demonstrated their high genome variability, which might be responsible for their difference in biofilm formation on the slippery BMA-EDMA surface. The results show that although the slippery BMA-EDMA surface has a great potential against biofilm formation, the generality of its bacteria resistant properties is still to be improved. © 2013 American Chemical Society.


Wang Z.,Institute of Functional Interfaces | Liu J.,Institute of Functional Interfaces | Arslan H.K.,Institute of Functional Interfaces | Grosjean S.,Institute of Biological Interfaces | And 5 more authors.
Langmuir | Year: 2013

In this work, we demonstrate that strain-promoted azide-alkyne cycloaddition (SPAAC) yields virtually complete conversion in the context of the post-synthetic modification (PSM) of metal-organic frameworks (MOFs). We use surface-anchored MOF (SURMOF) thin films, [Zn2(N3-bdc) 2(dabco)], grown on modified Au substrates using liquid-phase epitaxy (LPE) as a model system to first show that, with standard click chemistry, presently, the most popular method for rendering additional functionality to MOFs via PSM, quantitative conversion yields, cannot be reached. In addition, it is virtually impossible to avoid contaminations of the product by the cytotoxic CuI ions used as a catalyst, a substantial problem for applications in life sciences. Both problems could be overcome by SPAAC, where a metal catalyst is not needed. After optimization of reaction conditions, conversion yields of nearly 100% could be achieved. The consequences of these results for various applications of PSM-modified SURMOFs in the fields of membranes, optical coatings, catalysis, selective gas separation, and chemical sensing are briefly discussed. © 2013 American Chemical Society.


News Article | February 15, 2017
Site: phys.org

Researchers of Karlsruhe Institute of Technology (KIT) have made major progress in the production of two-dimensional polymer-based materials. To produce cloths from monomolecular threads, the scientists used SURMOFs, i.e. surface-mounted metal-organic frameworks, developed by KIT. They inserted four-armed monomers, i.e. smaller molecular building blocks, into some SURMOF layers. Cross-linking of the monomers then resulted in textiles consisting of interwoven polymer threads. Self-organized cross-linking of polymer threads, i.e. of extremely long molecules, to two-dimensional tissues is a big challenge in polymer chemistry. With the help of a bottom-up process to cross-link smaller molecules, so-called monomers, scientists of the Institute of Functional Interfaces (IFG) and Institute of Nanotechnology (INT) of KIT now made an important step towards reaching this objective. They produced a tissue from monomolecular polymer threads by using SURMOFs, i.e. surface-mounted metal-organic frameworks, as looms. This approach is now presented in Nature Communications. The SURMOFs developed by IFG are frameworks consisting of metallic node points and organic linkers that are assembled on a substrate layer by layer. They have a crystalline structure and can be customized to a large range of the applications by combining various materials and varying the pore sizes. For weaving two-dimensional textiles, the KIT scientists specifically inserted special connection elements, i.e. four-armed monomers, into the SURMOF layers for later cross-linking. Then, these active SURMOF layers were embedded between so-called sacrificial layers. "In this way, we produced a sandwich-type setup to ensure that the textiles produced really are two-dimensional, which means that they have a thickness of one molecule layer only," Professor Christof Wöll says. He heads the IFG and is the corresponding author of the publication together with Professor Marcel Mayor of INT. The scientists then applied a catalyst in these active SURMOF layers to start a reaction for linking the monomers to polymers. Afterwards, the metallic node points were removed. Flat tissues of monomolecular polymer threads remained. "The polymer threads are kept together by the mechanical forces resulting from the weave pattern," Marcel Mayor explains. "Hence, the molecular tissues are as flexible as textiles produced in a conventional way." Explore further: Improving the mechanical properties of polymer gels through molecular design More information: Zhengbang Wang et al. Molecular weaving via surface-templated epitaxy of crystalline coordination networks., Nature Communications (2017). DOI: 10.1038/ncomms14442


News Article | December 28, 2016
Site: www.cemag.us

Researchers of Karlsruhe Institute of Technology (KIT) and Universität Hannover developed novel membranes, whose selectivity can be switched dynamically with the help of light. For this purpose, azobenzene molecules were integrated into membranes made of metal-organic frameworks (MOFs). Depending on the irradiation wavelength, these azobenzene units in the MOFs adopt a stretched or angular form. In this way, it is possible to dynamically adjust the permeability of the membrane and the separation factor of gases or liquids. The results are reported in Nature Communications. Metal-organic frameworks, MOFs for short, are highly porous crystalline materials, consisting of metallic nodes and organic linkers. They can be tailored to many different applications. Among others, they have an enormous potential as membranes for efficient separation of molecules according to various parameters. By modifying pore sizes and chemical properties of the pore walls, static selectivity of the membranes can be adapted to the respective requirements. In Nature Communications the scientists for the first time present membranes, whose selectivities can be tuned dynamically. This is done remotely with the help of light. Researchers of KIT’s Institute of Functional Interfaces (IFG) and Institute of Organic Chemistry (IOC), in cooperation with scientists of Leibniz Universität Hannover, equipped MOF-based membranes with photoswitches. “In this way, the membranes are provided with minute windows that open and close depending on light irradiation,“ the Head of the Institute of Functional Interfaces, Professor Christof Wöll, explains. Azobenzene molecules are used as remote-controlled photoswitches. They consist of two phenyl rings each, which are linked by a nitrogen double bond. Two different configurations exist: A stretched trans-configuration and an angular cis-configuration. Irradiation with light causes the molecule to reposition. Under visible light the molecule stretches, under UV light it bends. Repositioning is reversible, can be repeated as often as desired, and does not affect the crystalline structure of the MOFs. Precise control of the ratio between cis- and trans-azobenzene by e.g. a precisely adjusted irradiation time or simultaneous irradiation with UV light and visible light enables dynamic tuning of membrane permeability and of separation efficiency of gaseous or liquid substance mixtures. “Control of these important properties by external stimuli, i.e. without having direct contact with the membrane, is a real breakthrough in membrane technology “, says Dr. Lars Heinke, Head of the IFG Group ”Dynamic Processes in Porous Systems.“ Functioning of the novel smart membranes was demonstrated by the separation of a hydrogen-carbon dioxide gas mixture. The scientists succeeded in dynamically tuning the separation factor between three and eight. The concept is also suited for separating other gas mixtures, such as nitrogen-carbon dioxide mixtures. It might also be feasible to use MOF membranes with photoswitches to control accessibility of catalyst or sensor surfaces or release of encapsulated medical substances.


News Article | December 23, 2016
Site: phys.org

A MOF membrane with integrated photoswitches separates molecules. The sepa-ration factor can be tuned dynamically by light irradiation. Credit: Alexander Knebel/Universität Hannover and Lars Heinke/KIT Researchers of Karlsruhe Institute of Technology (KIT) and Uni-versität Hannover developed novel membranes, whose selectivity can be switched dynamically with the help of light. For this pur-pose, azobenzene molecules were integrated into membranes made of metal-organic frameworks (MOFs). Depending on the irradiation wavelength, these azobenzene units in the MOFs adopt a stretched or angular form. In this way, it is possible to dynamically adjust the permeability of the membrane and the separation factor of gases or liquids. The results are reported in Nature Communications. Metal-organic frameworks, MOFs for short, are highly porous crys-talline materials, consisting of metallic nodes and organic linkers. They can be tailored to many different applications. Among others, they have an enormous potential as membranes for efficient separa-tion of molecules according to various parameters. By modifying pore sizes and chemical properties of the pore walls, static selectiv-ity of the membranes can be adapted to the respective require-ments. In Nature Communications the scientists for the first time present membranes, whose selectivities can be tuned dynamically. This is done remotely with the help of light. Researchers of KIT's Institute of Functional Interfaces (IFG) and Institute of Organic Chemistry (IOC), in cooperation with scientists of Leibniz Universität Hannover, equipped MOF-based membranes with photoswitches. "In this way, the membranes are provided with minute windows that open and close depending on light irradiation," the Head of the Institute of Functional Interfaces, Professor Christof Wöll, explains. Azobenzene molecules are used as remote-controlled photoswitch-es. They consist of two phenyl rings each, which are linked by a nitrogen double bond. Two different configurations exist: A stretched trans-configuration and an angular cis-configuration. Irra-diation with light causes the molecule to reposition. Under visible light the molecule stretches, under UV light it bends. Repositioning is reversible, can be repeated as often as desired, and does not affect the crystalline structure of the MOFs. Precise control of the ratio between cis- and trans-azobenzene by e.g. a precisely adjusted irradiation time or simultaneous irradiation with UV light and visible light enables dynamic tuning of membrane permeability and of separation efficiency of gaseous or liquid sub-stance mixtures. "Control of these important properties by external stimuli, i.e. without having direct contact with the membrane, is a real breakthrough in membrane technology ", says Dr. Lars Heinke, Head of the IFG Group "Dynamic Processes in Porous Systems." Functioning of the novel smart membranes was demonstrated by the separation of a hydrogen-carbon dioxide gas mixture. The sci-entists succeeded in dynamically tuning the separation factor be-tween three and eight. The concept is also suited for separating other gas mixtures, such as nitrogen-carbon dioxide mixtures. It might also be feasible to use MOF membranes with photoswitches to control accessibility of catalyst or sensor surfaces or release of encapsulated medical substances. Explore further: Scientists work out method to create unique polymeric membranes with carbon nanotubes More information: Zhengbang Wang et al. Tunable molecular separation by nanoporous membranes, Nature Communications (2016). DOI: 10.1038/ncomms13872


Gorniak T.,University of Heidelberg | Heine R.,University of Heidelberg | Mancuso A.P.,German Electron Synchrotron | Staier F.,University of Heidelberg | And 17 more authors.
Optics Express | Year: 2011

The imaging of hydrated biological samples - especially in the energy window of 284-540 eV, where water does not obscure the signal of soft organic matter and biologically relevant elements - is of tremendous interest for life sciences. Free-electron lasers can provide highly intense and coherent pulses, which allow single pulse imaging to overcome resolution limits set by radiation damage. One current challenge is to match both the desired energy and the intensity of the light source. We present the first images of dehydrated biological material acquired with 3rd harmonic radiation from FLASH by digital in-line zone plate holography as one step towards the vision of imaging hydrated biological material with photons in the water window. We also demonstrate the first application of ultrathin molecular sheets as suitable substrates for future free-electron laser experiments with biological samples in the form of a rat fibroblast cell and marine biofouling bacteria Cobetia marina. ©2011 Optical Society of America.

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